The way you described calculating change is essentially the method taught in common core. Common core is not about efficiency, it's about helping kids develop

The way you described calculating change is essentially the method taught in common core. Common core is not about efficiency, it's about helping kids develop an intuitive understanding of how numbers work. It turns out that a lot of children who learned how to subtract on paper with borrowing never learn how to do math in their head the way you described. Common core is an attempt to correct that deficiency.